Influence of Abiotic Stress on Molecular Responses of Flowering in Rice

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Rice is a short-day plant, and its heading date (Hd)/flowering time is one of the important agronomic traits for realizing the maximum yield with high nutrition. Theoretically, flowering initiates with the transition from the vegetative stage to shoot apical meristems (SAMs), and it is regulated by endogenous and environmental signals. Under favorable environmental conditions, flowering is triggered with the synthesis of mobile signal florigen in leaves and then translocated to the shoot for activation of cell differentiation-associated genes. In rice, the genetic pathway of flowering comprises OsGI–Hd1–Hd3a, which is an ortholog of the Arabidopsis GI–CO–FT pathway, and the Ehd1-Hd3a pathway. Climate change could affect photoperiod and temperature, which in turn influences heading date and crop yield. In low temperatures and long-day conditions, the expression of the HD3a gene analogous to FT in Arabidopsis deceased, which delays flowering. Similarly, during drought, expression of the Ehd1 gene is suppressed, resulting in a late-flowering phenotype in rice. Drought affects pollen fertility and reduction in grain yield by reducing male fertility, which affects male meiosis during reproduction, microspore development, and anther dehiscence. In this research field, substantial progress has been made to manipulate flowering-related genes to combat abiotic stresses. Here, we summarize the roles of a few genes in improving the flowering traits of rice.